The present application is related to devices and methods for injecting suspended solids into a body. Specifically, the present invention is related to a hypodermic needle assembly and hub having a curvedly tapered lumen and higher pressure Luer-lock fittings for joining syringes to hypodermic needles, and methods for using same.
Hypodermic needles are commonly used to inject fluids into a body. It will be understood that injection of fluids occurs both with respect to human bodies and animal bodies. While the present invention, in its preferred embodiment, is intended for use in injecting fluids into a human body, veterinary applications are specifically contemplated. The needles have a sharpened distal end and often have a hub fitting on the proximal end for mating to a syringe. The fitting is often a Luer fitting, which describes generally the male-female shapes of the syringe and needle hub, respectively. When the Luer fitting includes means such as threads for locking the male and female parts together, the fitting is known as a Luer-lock tip. The Luer-lock fitting is a standard fitting in the medical field, often having a single thread having nominally three turns about the longitudinal axis of the syringe. The Luer-lock fitting is well suited for administering agents such as drugs through common hypodermic needle lengths.
A composition and method for treating urinary incontinence is described in related U.S. patent application Ser. No. 08/676,592, filed Jul. 8, 1996, entitled IMPROVED TISSUE INJECTABLE COMPOSITION AND METHOD OF USE, herein incorporated by reference. The composition includes solid particles having an average size of between about 100 and 1,000 microns, preferably between 200 and 500 microns. The particles can be carried in a suspension such as a fluid or gel.
Standard Luer-lock fittings have been used to inject the particles into a body through the employment of endoscopes, but with less than optimal results due in part to problems related to the particular application. One problem is the long needle lengths required for the application. Needle lengths are dictated both by anatomy and by the length of endoscopes used in the procedures. Needles used in injecting solids into the urinary sphincter muscles are nominally 16 inches long. Needles used in injecting solids into esophageal sphincter can be about 60 inches long. The longer internal paths have a higher resistance to flow than the shorter paths typically found in hypodermic needles.
Another problem is related to the nature of the injected composition. The injectable material includes solid particles suspended in a carrier, such as a gel. A typical Luer-lock fitting includes a lumen having a large inside diameter proximal end and a smaller inside diameter distal end. The transition from large inside diameter to small inside diameter can be a step change or a straight taper, as the shapes are easy to mold and manufacture. These transition taper shapes work well with typical liquids, but work less than optimally with large particles suspended in a liquid carrier. In particular, the particles can be swept along a straight taper region to a location immediately proximal of the small inside diameter portion, and become bunched up at this point. The particles massed at one point can prevent the further passage of any particles. What would be desirable is a Luer-lock fitting better able to lessen the blockage by the large particles.
Still another problem with conventional Luer-lock fittings is the use of a single thread. Attempting to force large, possibly bunched, suspended particles suspended in a viscous carrier through long hypodermic needles can require high pressure. In practice, this can require a great deal of hand pressure on the plunger of a syringe. In practice, this high pressure can result in fluid leakage at the Luer-lock fitting. The loss of the fluid can be a significant problem, as it serves as the carrier for the particles. With loss of the carrier in the Luer-lock fitting, the particles become more concentrated, and less likely for flow through the fitting and into the hypodermic needle lumen. What would be desirable is a fitting better able to withstand the high pressures required to inject suspended solids through hypodermic needles.
The present invention includes a hypodermic needle having an improved Luer-lock fitting for injection of suspended solids through the needle. The present invention includes methods for using the improved fitting to inject solid particles suspended in a viscous carrier through long hypotube sections and into soft tissue to treat deficiencies. Applicants believe the present invention reduces the blockage of Luer fittings by large, suspended solid particles. Applicants also believe the present invention provides a fitting better able to withstand the higher pressures applied when injecting viscous suspensions through long hypotube sections.
One improved fitting according to the present invention includes a substantially cylindrical or tubular hub body affixed to the proximal end of a hypodermic needle. The hub body has a proximal end for receiving fluid, a distal end for ejecting fluid, a lumen therethrough, and a hub body wall having a threaded region. The body includes a region having a curvedly tapered inside diameter, decreasing the inside diameter with increasing distal position. The curved taper region is preferably disposed distally of a standard, straight, Luer tapered region. The curved taper is believed to reduce the likelihood of blockage from particles bunching up near the taper distal end. Blockages have been observed in Luer fittings having straight tapers. Such blockages can preclude further particle flow and can cause large back pressures. Applicants believe even small blockages can preferentially allow flow of a suspension fluid over flow of suspended particles, concentrating the particles in less fluid until the blockage becomes more pronounced.
A preferred embodiment has more than a single thread, providing a tighter, pressure resistant seal between syringe and Luer-lock fitting. One fitting has two start threads 180 degrees opposed, each wrapping around the fitting for about 1 and xc2xd turns. One fitting hub has two opposed wings extending outward from the longitudinal axis of the hub. The wings provide a structure for tightly grasping and turning the hub relative to the syringe. Preferred wings have a rounded periphery. The rounded wings can deflect objects striking the wings, lessening the force which can act to dislodge a positioned hypodermic needle. In particular, the rounded wings can deflect an endoscope eyepiece knocking against the hub.
In use, a long hypodermic needle having a Luer-lock hub according to the present invention is provided. A suspension of solids in a liquid carrier is provided in a syringe adapted to mate to the Luer-lock fitting. The syringe is secured to the Luer-lock fitting at a point in time as dictated by the user. In one method, the syringe is secured before advancing the needle into the patient. In another method, the syringe is secured only after the needle tip has been advanced close to the target site. The needle is preferably advanced through an endoscope such that the sharp needle tip is visualized as the tip is advanced.
The sharp needle tip can be advanced until the target site is penetrated, and the syringe plunger depressed until a sufficient amount of solid suspension has been injected into the target. The needle can be retracted and advanced to different target sites until the area has been treated. A preferred use of the present invention is the augmentation of urinary, anal and gastric sphincter mechanisms with injected solid particles.